Collapsible helical antenna

ABSTRACT

A collapsible helical antenna formed of an extensible boom made of preferably two coiled flat steel ribbons which, when uncoiled, become tubular one inside the other and formed of a helical conductor that is suspended coaxially from the boom by a plurality of rings disposed around the boom and tied together by flexible members and by tensioned members extending from the rings to the helical conductor so that, as the boom is extended, the rings slide along the boom to become separated a distance determined by the flexible members but the helical wire is still maintained coaxial with the boom.

United States Patent Morrison [54] COLLAPSIBLE HELICAL ANTENNA [72]Inventor: Adrian O. Morrison, Tustin, Calif.

[73] Assignee: North American Rockwell Corporation 22 Filed: Dec.17,1970

[21] Appl.No.:99,'172

[52] US. Cl ..343/880, 343/895 [51] Int. Cl. ..H01q 1/36 [58] Field ofSearch ..343/895, 880

[56] References Cited UNITED STATES PATENTS 3,524,193 8/1970 Auletta..343/895 2,613,319 10/1952 Lisbin et al. ..343/823 3,541,568 11/1970Lowenhar ..343/877 FOREIGN PATENTS OR APPLICATIONS 810,325 12/1936France ..343/895 51 Oct. 17,1972

Primary Eicaminer--Eli Lieberman Attorney-L. Lee l-lumphries, Charles F.Dischler and Dominick Nardelli [5 7] ABSTRACT A collapsible helicalantenna formed of an extensible boom made of preferably two coiled flatsteel ribbons which, when uncoiled, become tubular one inside the otherand formed of a helical conductor that is suspended coaxially from theboom by a plurality of rings disposed around the boom and tied togetherby flexible members and by tensioned members extending from the rings tothe helical conductor so that, as the boom is extended, the rings slidealong the boom to become separated a distance determined by the flexiblemembers but the helical wire is still maintained coaxial with the boom.

11 Claims, 5 Drawing Figures PATENIED [IN 1 7 I972 3 Sheets-Sheet 1INVENTOR. ADRIAN O. MORRISON ATTOP'VEY pmmgnum 11 I972 3 Sheets-Sheet 5INVENTOR.

ADRIAN 0. MORRISON ATTORNEY COLLAPSIBLE HELICAL ANTENNA FIELD OFINVENTION This invention relates to an extensible antenna and,

more particularly, to an extensible antenna of the helical type.

BACKGROUND OF THE INVENTION OBIECTS OF THE INVENTION An object of thisinvention is to provide a helical antenna which is light in weight andwhich is collapsible from its operative or extended position for ease ofportability.

Another object of this invention is to accomplish the foregoingeconomically and with sufficient dimensional accuracy and structuralrigidity to meet the stringent requirements imposed on helical antennas.

Another object of this invention is to provide a boom which isextensible and still provides the maximum possible rigidity.

These and other objects and features of advantage will become moreapparent after reading the following description of the preferredembodiment of the invention taken together with the drawings.

BRIEF DESCRIPTION OF THE VIEWS AND DRAWINGS FIG. 1 is an elevation of acollapsible helical antenna in the extended position and incorporatingthe features of the invention;

FIG. 2 is an enlarged elevation view of a few of the turns of the helix;

FIG. 3 is an enlarged elevation and partial section of the antenna inFIG. 1 in the collapsed position;

FIG. 4 is an end elevation view of the antenna taken on line 44 in FIG.3 and in the direction of the arrows; and

FIG. 5 is a plan view in section of a portion of the antenna takensubstantially on line 55 in FIG. 3 and in the direction of the arrows.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to thedrawings and to FIG. 1, in particular, a collapsible helical antenna isshown in the extended position and having a boom 11 supported by a post12 from a suitable structure 13. Around the boom 11 is disposed ahelical conductor 14 having a coupling wire 16 extending from thehelical conductor 16 to the structure 13. The conductor 14 is suspendedcoaxially from the boom by insulating tension members to be describedmore fully hereinafter. The coupling wire 16 is supported from the post12 by one or more insulators l7.

Referring to FIGS. 2, 3, and 4, the insulating tension members mentionedabove are more clearly illustrated. On boom 11 are disposed a pluralityof rings 21a, 21b, and 210. Each one of the rings 21a, 21b, and 21c arepreferably made of nylon which is a long chain polymeric amide havingre-occurring amide groups CONI-I as an integral part of the main polymerchain and which has the inherent property of being capable of slidingalong metallic surface under extreme weathering conditions for reasonsthat will become apparent hereinafter. All the rings,21a, 21b, 21c, areconnected one to the other by nylon flexible threads 22 all of equallength. The ends of threads 22 are suitably fixed to the rings as shownby suitable means. The threads 22 are disposed on opposite sides of theboom 11. The thread segments between adjacentrings are equal so that therings may be equally spaced along the boom. All the rings 21a haveattached thereto in a suitable manner nylon threads 23 at a point 23a onthe respective ring that is rotated from the point of attachment ofthreads 22. Threads 23 connectto points 14a on the helical conductor 14disposed radially outward from the points 23a and are of equal length.The threads 23 are arranged in a zig-zag arrangement wherein twosegments of threads 23 are attached at the same point 14a and at thesame point 23a. Rings 21b are attached to the conductor 14 by nylonthreads 24. However, attachment points 24a (FIG. 3) for threads 24 atthe rings 21b and attachment points 14b(FIG. 4) at the conductors 14 arerotated from the points of attachment points 14a and 23a of threads 23.Also, rings 210 are attached to the conductor by nylon threads 25.However, the attachment points 25a (FIG. 4) of threads 25 at rings 21cand attachment points 14c at the conductor 14 are rotated 120 from thepoints 14a and 23 a of threads 23 and also points 14b and 24a of threads24. Thus, the helical conductor 14 is supported rigidly coaxially withthe boom 11 because all nylon threads 23, 24, and 25 are of equallength.

Since the rings 21a, 21b, and 216 are capable of sliding axially alongthe boom 11, the helical conductor 14 is made to collapse to a positionas shown in FIG. 3 wherein the rings 21a, 21b, and 21c touch each other.Then, naturally, the segments of the threads 22 form loose loops asshown. The boom 11 is made of two relatively narrow, relatively longmetallic strips 31 and 32 as shown in FIGS. 4 and 5. Strips 31 and 32are made of, for example, beryllium copper sheets having a thickness ofa few thousandths of an inch and have been heat treated in a standardmanner as to cause each strip to assume a tubular shape. Due to theirfle xibility, the sheets 31 and 32 can be rolled upon spools such asspools 33 and 34, respectively. The spools 33 and 34 are journalledmounted within a suitable enclosure 36. The right end of enclosure 36,as viewed in FIG. 3, tapers down to a circular opening 37 through whichthe assembled boom 11 passes. The strips 31 and 32 are arranged so, asthey unwind from the respective spools, strip 31 assumes its tubularshape within the tubular shape assumed by strip 32. In addition, therespective edges meet each other at positions that are on opposite sidesof the boom 11 as shown in FIG. 4. The outer strip 31 can be made toassume a free diameter that is slightly smaller than the externaldiameter assumed by the inner strip 32. This causes the two strips tocome into more intimate contact making a more rigid boom. The post 12 isfixed to the enclosure 36 and, more specifically, to the lower sectionthereon as shown in FIG. 3. The boom 11 may be extended or retrieved byrotating one of the spools, for example spools 34, by suitable electricmotor 41 (FIG. 3) mounted below the enclosure. The left ends of thestrips are bonded together so that, as spool 34 rotates, both strips areextended or retracted together. As an alternative, the spools 33 and 34may be geared together in a suitable manner. To cause the helicalconductors to move with boom 11, the exterior ring 21a at the extremeleft end as viewed in FIG. 3 is bonded in a suitable manner to the outerstrip 31. Thus, both the boom and helix can be extended or retracted asrequired.

Although the preferred embodiment has been described, one understandsthat the description is made only by way of example and not as alimitation to the scope of the invention. The scope, therefore, islimited to the accompanying claims.

What is claimed is: 1. A collapsible, helical antenna comprising: aboom; a helical conductor disposed around said boom; a plurality ofrings disposed on said boom and in sliding relation therewith; firsttension elements extending from said rings to said helical conductor tohold said conductor coaxial to said boom; and flexible elements disposedto extend between adjacent ones of said rings for determining themaximum pitch of said helical conductor. 2. The antenna of claim 1wherein: said boom is extendable and retractable and comprises at leastone extendable resilient strip that is so fabricated so as to tend toform into an elongated tube, and when unrestrained has its longitudinalaxis lying parallel to the longitudinal centerline of the strip. 3. Theantenna of claim 2 wherein: said boom further includes another one ofsaid resilient strip; and said other one of said strips being disposedwithin the tubular form of said one strip when in the unrestrainedposition. 4. The antenna of claim 3 wherein: said boom is furtherdefined that the longitudinal edges of said one strip is disposedopposite the longitudinal edges of said other strip when said strips arein their tubular form; and

separate spools are provided for each strip to be rolled onto when saidboom is retracted.

5. The antenna of claim 4 wherein:

the free ends of said strips are bonded together; and

one of said rings that is disposed nearest the free ends is bonded tosaid one strip substantially adjacent the free end.

6. The antenna of claim 5 wherein:

two of said tension elements have one end respectively bonded at thesame point on one of said rings; and

two of said tension elements have the other end respectively bonded tothe same point on said conductor to form a zig-zag configuration whensaid antenna is extending.

7. The antenna of claim 1 wherein: said boom 15 extendable andretractable and comprises at least one extendable narrow resilient stripthat is so fabricated so as to tend to form into an elongated tube andwhen unrestrained .has its longitudinal axis lying parallel to thelongitudinal centerline of the strip.

8. The antenna of claim 7 wherein:

said boom further includes another one of said narrow, resilient strips;and

said other one of said strips being disposed within the tubular form ofsaid one strip when in the unrestrained position.

9. The antenna of claim 8 wherein:

said boom is further defined that the longitudinal edges of said onestrip is disposed opposite the longitudinal edges of said other stripwhen said strips are in their tubular form; and

separate spools are provided for each strip to be rolled onto when saidboom is retracted.

10. The antenna of claim 9 wherein:

the free end of said strips are bonded together; and

one of said rings, that is disposed nearest said free end, is bonded tosaid one strip substantially adjacent the free end thereof.

11. The antenna of claim 10 wherein:

two of said tension elements have one end respectively bonded at thesame point on one of said rings; and

two of said tension elements have the other end respectively bonded tothe same point on said conductor to form a zig-zag configuration whensaid antenna is extended.

1. A collapsible, helical antenna comprising: a boom; a helicalconductor disposed around said boom; a plurality of rings disposed onsaid boom and in sliding relation therewith; first tension elementsextending from said rings to said helical conductor to hold saidconductor coaxial to said boom; and flexible elements disposed to extendbetween adjacent ones of said rings for determining the maximum pitch ofsaid helical conductor.
 2. The antenna of claim 1 wherein: said boom isextendable and retractable and comprises at least one extendableresilient strip that is so fabricated so as to tend to form into anelongated tube, and when unrestrained has its longitudinal axis lyingparallel to the longitudinal centerline of the strip.
 3. The antenna ofclaim 2 wherein: said boom further includes another one of saidresilient strip; and said other one of said strips being disposed withinthe tubular form of said one strip when in the unrestrained position. 4.The antenna of claim 3 wherein: said boom is further defined that thelongitudinal edges of said one strip is disposed opposite thelongitudinal edges of said other strip when said strips are in theirtubular form; and separate spools are provided for each strip to berolled onto when said boom is retracted.
 5. The antenna of claim 4wherein: the free ends of said strips are bonded together; and one ofsaid rings that is disposed nearest the free ends is bonded to said onestrip substantially adjacent the free end.
 6. The antenna of claim 5wherein: two of said tension elements have one end respectively bondedat the same point on one of said rings; and two of said tension elementshave the other end respectively bonded to the same point on saidconductor to form a zig-zag configuration when said antenna isextending.
 7. The antenna of claim 1 wherein: said boom is extendableand retractable and comprises at least one extendable narrow resilientstrip that is so fabricated so as to tend to form into an elongated tubeand when unrestrained has its longitudinal axis lying parallel to thelongitudinal centerline of the strip.
 8. The antenna of claim 7 wherein:said boom further includes another one of said narrow, resilient strips;and said other one of said strips being disposed within the tubular formof said one strip when in the unrestrained position.
 9. The antenna ofclaim 8 wherein: said boom is further defined that the longitudinaledges of said one strip is disposed opposite the longitudinal edges ofsaid other strip when said strips are in their tubular form; andseparate spools are provided for each strip to be rolled onto when saidboom is retracted.
 10. The antenna of claim 9 wherein: the free end ofsaid strips are bonded together; and one of said rings, that is disposednearest said free end, is bonded to said one strip substantiallyadjacent the free end thereof.
 11. The antenna of claim 10 wherein: twoof said tension elements have one end respectively bonded at the samepoint on one of said rings; and two of said tension elements have theother end respectively bonded to the same point on said conductor toform a zig-zag configuration when said antenna is extended.